High-voltage device and medical-image diagnostic apparatus

ABSTRACT

A high-voltage device according to embodiments comprises an inverter circuit configured to convert a direct-current voltage into an alternating-current voltage, a high-voltage transformer, an insulating layer and a conductive layer. The high-voltage transformer includes a primary coil on an input side and multiple secondary coils on an output side and raises a voltage of output of the inverter circuit. The insulating layer is provided on an outer circumference of a bundle of winding wires of each of the secondary coils so as to individually cover each of the secondary coils The conductive layer is provided on an outer circumference of each of the insulating layers so as to individually cover each of the insulating layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-235987, filed on Dec. 5, 2016; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a high-voltage deviceand a medical-image diagnostic apparatus

BACKGROUND

With regard to a high-voltage generator, which is one of the elementsthat constitute an X-ray high-voltage device, included in an X-ray CTapparatus or an X-ray diagnostic apparatus, in order to reduce the sizeor ensure the dielectric strength voltage, its contents are immersed ininsulating oil or is hardened with insulating resin, or the like.Particularly, in X-ray CT apparatuses, as a high-voltage generator isplaced on a rotary gantry, all or some of the components, included inthe high-voltage generator, are often hardened with resin.

In this case, liquid resin is injected into the container that housesassembled and wired components and is then hardened. The resin injectionoperation is conducted in a vacuum, or a vacuum defoaming process isperformed after resin is injected. This is intended for reduction ofspaces, what are called voids, in which resin does not enter, as much aspossible. If a void is present in the hardened resin, there is apossibility that the electric field is concentrated (corona discharge)at the void at the time of generation of a high voltage and insulationbreakdown occurs. There is a problem in that, if an X-ray CT apparatus,an X-ray diagnostic apparatus, or the like, is used and insulationbreakdown occurs in the middle of diagnosis, the apparatus gets damagedand the diagnosis is interrupted.

As secondary winding wires of a high-voltage transformer in ahigh-voltage generator are wound closely due to a small wire diameter,resin is unlikely to penetrate between the wires. Furthermore, asparticulate or fiber-like material, called filler, is mixed to improvethe dielectric strength voltage or the radiation performance of resin,it is further difficult to permeate resin between the secondary windingwires of the high-voltage transformer without generating voids.

Furthermore, the relative permittivity of the above-described resin ishigher than that of vacuum, air, or insulating oil; therefore, if thesecondary winding wires of the high-voltage transformer are hardenedwith resin, the distributed capacitance between the secondary windingwires is increased. As the wattless current flows into the distributedcapacitance between the secondary winding wires, there is a problem inthat the wattless current in an inverter circuit, which drives thehigh-voltage generator, is increased so that the efficiency of the X-rayhigh-voltage device is lowered and the inverter circuit or thehigh-voltage transformer gets overheated. Furthermore, as an increase inthe distributed capacitance between the secondary winding wires causes adecrease in the resonance frequency of the high-voltage transformer, arise in the operating frequency of the inverter circuit is constrained,and a reduction in the size of the high-voltage generator isinterrupted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a high-voltage transformer accordingto an embodiment;

FIG. 2 is a cross-sectional view of the high-voltage transformer and ahigh-voltage rectifying-smoothing circuit according to the embodimentwith respect to the XY plane;

FIG. 3 is a cross-sectional view of the high-voltage transformer and thehigh-voltage rectifying-smoothing circuit according to the embodimentwith respect to the plane;

FIG. 4 is a diagram that illustrates a secondary coil, an insulatinglayer that covers it, and a conductive layer;

FIG. 5 is a diagram that illustrates another example of the secondarycoil, the insulating layer that covers it, and the conductive layer;

FIG. 6 is a diagram that illustrates another example of theconfiguration of a core that is included in the high-voltage transformeraccording to the embodiment;

FIG. 7 is a diagram that illustrates an example of the circuit structureof the X-ray high-voltage device according to the embodiment;

FIG. 8 is a diagram that illustrates an example of the circuit structureof the high-voltage generator of the X-ray high-voltage device accordingto the embodiment; and

FIG. 9 is a block diagram that illustrates an example of a medical-imagediagnostic apparatus that uses the X-ray high-voltage device accordingto the embodiment.

DETAILED DESCRIPTION

A high-voltage device according to embodiments comprises an invertercircuit, a high-voltage transformer, an insulating layer and aconductive layer. The inverter circuit is configured to convert adirect-current voltage into an alternating-current voltage. Thehigh-voltage transformer includes a primary coil on an input side andmultiple secondary coils on an output side and raises a voltage ofoutput of the inverter circuit. The insulating layer is provided on anouter circumference of a bundle of winding wires of each of thesecondary coils so as to individually cover each of the secondary coils.The conductive layer is provided on an outer circumference of each ofthe insulating layers so as to individually cover each of the insulatinglayers.

With reference to the drawings, an explanation is given below of thehigh-voltage device and a high-voltage generator according to anembodiment. Furthermore, an X-ray high-voltage device 6 is explainedbelow as an example of the high-voltage device. Moreover, high-voltagegenerators 71, 72 are explained below as examples of the high-voltagegenerator. In the following explanations, duplicated explanations areappropriately omitted.

With reference to FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6, anexplanation is given of the configurations of a high-voltage transformer618 and high-voltage rectifying-smoothing circuits 6191 and 6192. FIG. 1is a diagram that illustrates one of the high-voltage transformers 618according to the embodiment, which is cross-sectioned on the planeparallel to the ZX plane as viewed in −Y direction. The high-voltagetransformer 618 in FIG. 1 is a shell-type single-phase transformer, anda single primary coil 616 and n secondary coils I11 to I1 n arecoaxially wound around the center leg of a core 617. The core 617 inFIG. 1 is for example an EER-type ferrite core. The primary coil 616 iswound around a winding form 631 so as to be insulated from the core 617.The primary coil 616 is a coil on the input side, provided in thehigh-voltage transformer 618. An insulating film 632 and a shield plate633 are provided on the primary coil 616. The n secondary coils I11 toI1 n are covered with insulating layers 641 to 64 n, and furthermore theoutside of the insulating layers 641 to 64 n are covered with conductivelayers 651 to 65 n. The secondary coils I11 to I1 n are coils on theoutput side, provided in the high-voltage transformer 618.

FIG. 2 is a diagram of the high-voltage transformer 618 according to theembodiment and one of high-voltage rectifying-smoothing circuits 619 n,connected to the high-voltage transformer 618, which is cross-sectionedon the plane parallel to the XY plane when the inner side area of theresin is viewed in +Z direction. Although I1 n is explained as anexample among the n secondary coils in FIG. 2, the secondary coils I11to I1 n-1 also have the same structure. The winding start and thewinding end of the shield plate 633 are insulated with an insulatingfilm 634 so that they are prevented from being shunted. The high-voltagerectifying-smoothing circuit 619 n is connected to two terminals of thesecondary coil I1 n so that it rectifies and smooths the voltage, guidedinto the secondary coil I1 n, and outputs direct-current voltage toterminals 66 n and 67 n. In the example illustrated in FIG. 2, thesecondary coil I1 n and the high-voltage rectifying-smoothing circuit619 n are integrated and covered with the conductive layer 65 n;however, it is possible that the secondary coil I1 n and thehigh-voltage rectifying-smoothing circuit 619 n are separated and onlythe secondary coil I1 n is covered with the conductive layer 65 n.

FIG. 3 is a diagram of the high-voltage transformer 618 according to theembodiment and the high-voltage rectifying-smoothing circuits 6191 to619 n connected to the high-voltage transformer 618, which arecross-sectioned on the plane parallel to the YZ plane as viewed in +Xdirection. The output terminals of the high-voltage rectifying-smoothingcircuits 6191 to 619 n are cascade-connected, and a direct-current highvoltage is output at both ends of them. The high-voltagerectifying-smoothing circuits 6191 to 619 n may be configured by usingCockcroft-Walton circuits, voltage-doubler rectifying circuits, orfull-wave rectifying circuits. The conductive layers 651 to 65 n arecovered with resin PL so as to be insulated from the core 617, theprimary coil 616, and the shield plate 633.

As illustrated in FIG. 1, FIG. 2, and FIG. 3, the insulating layer 641to the insulating layer 64 n cover the secondary coil I11 to thesecondary coil I1 n, respectively. That is, the insulating layer 641 tothe insulating layer 61 n are containers that are made of insulatingmaterial and that house the secondary coil I11 to the secondary coil I1n, respectively. Alternatively, the insulating layer 641 to theinsulating layer 64 n are hollow members that are made of insulatingmaterial and that house the secondary coil I11 to the secondary coil I1n, respectively.

These insulating layers are formed by for example immersing a secondarycoil in melted resin. Alternatively, these insulating layers are formedby attaching thermo-setting resin powder to a secondary coil and heatingit. Furthermore, if these methods are implemented in 1 atmosphere,depressurized atmosphere, or inert gas, air or inert gas may remainbetween winding wires of the secondary coil I11 to the secondary coil I1n.

Furthermore, the insulating layer 641 to the insulating layer 64 n maycover the high-voltage rectifying-smoothing circuit 6191 to thehigh-voltage rectifying-smoothing circuit 619 n, respectively, inaddition to the secondary coil I11 to the secondary coil I1 n. Moreover,the insulating layer 641 to the insulating layer 64 n may cover thehigh-voltage rectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n, respectively, instead of thesecondary coil I11 to the secondary coil I1 n.

Furthermore, an insulating layer may be provided in at least one of thegaps between the conductive layer 651 and the high-voltagerectifying-smoothing circuit 6191, the conductive layer 6 and thehigh-voltage rectifying-smoothing circuit 2, and to the conductive layer65 n and the high-voltage rectifying-smoothing circuit 619 n.

As illustrated in FIG. 3, FIG. 4, and FIG. 5, the conductive layer 651to the conductive layer 65 n are conductive hollow members. Theconductive layer 651 to the conductive layer 65 n house the secondarycoil I11 and the high-voltage rectifying-smoothing circuit 6191 to thesecondary coil I1 n and the high-voltage rectifying-smoothing circuit619 n, respectively. That is, as illustrated in FIG. 5, the conductivelayer 651 to the conductive layer 65 n are provided to cover thesecondary coil I11 and the high-voltage rectifying-smoothing circuit6191 to the secondary coil I1 n and the high-voltagerectifying-smoothing circuit 619 n, respectively. Furthermore, in otherwords, as illustrated in FIG. 5, the conductive layer 651 to theconductive layer 65 n are provided to cover the entire surface of thesecondary coil I11 and the high-voltage rectifying-smoothing circuit6191 to the secondary coil I1 n and the high-voltagerectifying-smoothing circuit 619 n, respectively.

Furthermore, as illustrated in FIG. 3, FIG. 4, and FIG. 5, theconductive layer 651 to the conductive layer 65 n house the insulatinglayer 641 to the insulating layer 64 n, respectively. Specifically, asillustrated in FIG. 3, FIG. 4, and FIG. 5, the conductive layer 651 tothe conductive layer 65 n are provided to cover the insulating layer 641to the insulating layer 64 n, respectively. Furthermore, in other words,as illustrated in FIG. 3, FIG. 4, and FIG. 5, the conductive layer 651to the conductive layer 65 n are provided to cover the entire surface ofthe insulating layer 641 to the insulating layer 64 n, respectively.That is, the conductive layer 651 and the conductive layer 652 to theconductive layer 65 n are formed on the outside of the respectiveinsulating layers.

Furthermore, the conductive layer 651 to the conductive layer 65 n mayinclude a hollow area to house the secondary coil I11 to the secondarycoil I1 n, respectively, and a hollow area to house the high-voltagerectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n, respectively.

Furthermore, the conductive layer 651 to the conductive layer 65 n mayhouse only the secondary coil I11 to the secondary coil I1 n,respectively. That is, the conductive layer 651 to the conductive layer65 n may be provided to cover only the secondary coil I11 to thesecondary coil I1 n, respectively. Furthermore, in other words, theconductive layer 651 to the conductive layer 65 n may be provided tocover the entire surface of only the secondary coil I11 to the secondarycoil I1 n, respectively. Alternatively, the conductive layer 651 to theconductive layer 65 n may house only the high-voltagerectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n, respectively. That is, theconductive layer 651 to the conductive layer 65 n may cover only thehigh-voltage rectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n, respectively.

Here, if the conductive layer 651 to the conductive layer 65 n cover thehigh-voltage rectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n, respectively, the conductive layer651 to the conductive layer 65 n are electrically connected to a singlepoint of the high-voltage rectifying-smoothing circuit 6191 to thehigh-voltage rectifying-smoothing circuit 619 n, respectively.

Specifically, the conductive layer 651 to the conductive layer 65 n areelectrically connected to the terminals that are closer to the groundvoltage among the output terminals of the high-voltagerectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n.

The conductive layer 651 to the conductive layer 65 n only have to beconductive. Therefore, the conductive layer 651 to the conductive layer65 n are membranes that are made of resin in which, for example,metallic membranes or carbon is impregnated. Furthermore, the metallicmembrane is formed by for example vapor deposition. Furthermore,membranes made of resin in which, carbon is impregnated, are formed byfor example applying resin including carbon to each insulating layer.

As illustrated in FIG. 5, FIG. 4, and FIG. 5, the circumferences of theconductive layer 651 to the conductive layer 65 n are filled with theresin PL.

FIG. 4 is an enlarged view of the secondary coil I1 n, the insulatinglayer 64 n that covers it, and the conductive layer 65 n in FIG. 1. Theinsulating layer 64 n, which is like a thin membrane, is providedoutside the secondary coil I1 n, and the conductive layer 65 n, which islike a thin membrane, is further provided outside it. There is a voidspace between winding wires of the secondary coil I1 n, and dry air orinert gas is present. As there is no resin between winding wires of thesecondary coil fin, inter-winding distributed capacitance may bereduced. In FIG. 4, self-fusing electric wires are used as the windingwires of the secondary coil I1 n so that a bobbin is not necessary. Asanother method for implementing the insulating layer 64 n and theconductive layer 65 n, there is also a method by which the secondarycoil I1 n is housed in a thin resin case, the outside of which issubjected to conductive coating or conductive processing due to metaldeposition, or the like, as in FIG. 5. Alternatively, there is also amethod by which the secondary coil I1 n is housed in a case that is madeof resin that is conductive after being mixed with carbon, or the like.In this case, winding-wire covering of the secondary coil I1 n forms aninsulating layer. The resin case may also be used as a bobbin which thesecondary coil I1 n is wound around. Furthermore, the secondary coil I11to the secondary coil I1 n-1 also have the same structure.

FIG. 6 illustrates the core shape if the core made of, for example,silicon steel, oriented magnetic steel, amorphous magnetic material, ornanocrystalline magnetic material is used instead of the core 617 thatis made of ferrite. In this case, U-U cores 617 a and 617 b form cores.They are also called cut cores as they are manufactured by being cutinto two after a strip-shaped core material is wound around a form. Ifthe cut core is used, the core cross-sectional surface is typicallyrectangular, and therefore the coil is sometimes wound in a rectangularshape.

With reference to FIG. 7, the circuit structure the X-ray high-voltagedevice 6 according to the embodiment is explained. As illustrated inFIG. 7, the X-ray high-voltage device 6 receives the voltage of thethree-phase alternating-current power source AC as an input and suppliesa positive direct-current high voltage and a negative direct-currenthigh voltage to an X-ray tube 7. The X-ray tube 7 is a neutral-groundingtype, and it applies a positive direct-current high voltage to the anodeand a negative direct-current high voltage to the cathode.

The X-ray high-voltage device 6 include an AC/DC converter circuit 60,two inverter circuits 61, 62, two coils 615, 625, and the twohigh-voltage generators 71, 72. The AC/DC converter circuit 60 includesa three-phase rectifying diode bridge 601 and a smoothing capacitor 602.The inverter circuit 61 includes a rail capacitor 610 and switchingelements 611 to 614. The switching elements 611 to 614 are controlled soas to be on/off by undepicted control circuitry so that they convert adirect-current voltage into an alternating-current voltage. The invertercircuit 62 includes a rail capacitor 620 and switching elements 621 to624. The switching elements 621 to 624 are controlled so as to be on/offby undepicted control circuitry so that they convert a direct-currentvoltage into an alternating-current voltage. Specifically, the gates ofthe switching elements 611 to 624 are controlled so as to be on/off byundepicted control circuitry so that they convert a direct-currentvoltage into an alternating-current voltage. In the illustrated example,the switching elements 611 to 614 and the switching elements 621 to 624are the inverse-parallel circuit of diodes and the Insulated GateBipolar Transistor (IGBT); however, instead of the IGBT, bipolartransistor, power MOSFET, Junction FET, or the like, may be used. Thehigh-voltage generator 71 includes the high-voltage transformer 618 andthe high-voltage rectifying-smoothing circuits 6191 to 619 n. Similarly,the high-voltage generator 72 includes a high-voltage transformer 628and high-voltage rectifying-smoothing circuits 6291 to 629 n. Thehigh-voltage transformer 628 is a hell-type single-phase transformer,and a single primary coil 626 and n secondary coils I21 to I2 n arecoaxially wound around the center leg of a core 627. The primary coil626 is a coil on the input side, provided in the high-voltagetransformer 628. The secondary coils I21 to I2 n are coils on the outputside, provided in the high-voltage transformer 628. Furthermore, thecore 627 is an EER-type ferrite core. In the example illustrated in FIG.7, the high-voltage rectifying-smoothing circuits 6191 to 619 n and thehigh-voltage rectifying-smoothing circuits 6291 to 629 n are two-stageCockcroft-Walton circuit; however, a full-wave rectifying circuit or avoltage-doubler rectifying circuit may be used. The coil 615 isconnected between the inverter circuit 61 and the high-voltage generator71. Instead of the coil 615, leakage inductance of the high-voltagetransformer 618 may be used. The coil 625 is connected between theinverter circuit 62 and the high-voltage generator 72. Instead of thecoil 625, leakage inductance of the high-voltage transformer 628 may beused.

Each of the high-voltage rectifying-smoothing circuits 6191 to 619 n inthe high-voltage generator 71 outputs a positive direct-current voltage,and the outputs are cascade-connected. The minus output terminal of thehigh-voltage rectifying-smoothing circuit 6191 is grounded, and apositive direct-current high voltage is obtained at the plus outputterminal of the high-voltage rectifying-smoothing circuit 619 n. In thesame manner, each of the high-voltage rectifying-smoothing circuits 6291to 629 n in the high-voltage generator 72 outputs a negativedirect-current voltage, and the outputs are cascade-connected. The plusoutput terminal of the high-voltage rectifying-smoothing circuit 6291 isgrounded, and a negative direct-current high voltage is obtained at theminus output terminal of the high-voltage rectifying-smoothing circuit629 n.

In FIG. 7, the high-voltage generator 71, which generates a positivehigh voltage, and the high-voltage generator 72, which generates anegative high voltage, are separated; however, they may be combined tobe a single high-voltage generator.

If the inverter circuit 61 and the inverter circuit 62 are operated witha phase shift of 90°, ripple of the voltage applied to the X-ray tube 7may be reduced. Furthermore, if the polarities of the secondary windingwires of the high-voltage transformer 618 and the high-voltagetransformer 629 are alternately reversed, ripple of the voltage appliedto the X-ray tube 7 may be further reduced.

FIG. 8 is a circuit diagram that illustrates a high-voltage generator 73and the X-ray tube 7 in the X-ray high-voltage device for theanode-grounded type X-ray tube. High-voltage rectifying-smoothingcircuits 6891 to 689 n and the high-voltage rectifying-smoothingcircuits 6291 to 629 n output a negative direct-current voltage. All ofthem are cascade-connected, the plus output terminal of the high-voltagerectifying-smoothing circuit 6891 is grounded, and a negativedirect-current high voltage is obtained at the minus output terminal ofthe high-voltage rectifying-smoothing circuit 629 n. The anode of theX-ray tube 7 is grounded, and a negative direct-current high voltage isapplied to its cathode.

As is the case with the circuit in FIG. 7, if the inverter circuits fordriving a high-voltage transformer 688 and the high-voltage transformer628 are operated with a phase shift of 90°, ripple of the voltageapplied to the X-ray tube 7 may be reduced. Furthermore, if thepolarities of the secondary winding wires of the high-voltagetransformer 688 and the high-voltage transformer 628 are alternatelyreversed, ripple of the voltage applied to the X-ray tube 7 may befurther reduced. Here, as illustrated in FIG. 8, the high-voltagetransformer 688 includes a primary coil 686, a core 687, and secondarycoils I81 to I8 n.

The X-ray high-voltage device 6 may include one or three or moreinverters. The X-ray high-voltage device 6 may supply the alternatingcurrent to a primary coil of a single high-voltage transformer by usinga single inverter. Alternatively, the X-ray high-voltage device 6 maysupply the alternating current to primary coils of high-voltagetransformers by using a single inverter.

Next, the advantage of the conductive layer 651 to the conductive layer65 n is explained.

The conductive layer 65 n covers all the spaces between the windingwires of the secondary coil I1 n. Furthermore, the conductive layer 65 nis conductive. Therefore, the electric potential of the entireconductive layer 65 n has a single value. Thus, all the spaces betweenthe winding wires of the secondary coil I1 n do not receive applicationof the voltage without regard for the environment outside the conductivelayer 65 n. Thus, the conductive layer 65 n may prevent damages to theX-ray high-voltage device 6 due to corona discharge that occurs in eachspace between winding wires of the secondary coil I1 n. The same holdsfor the conductive layer 651, the conductive layer 652, or the like.

Furthermore, in the high-voltage generators 71, 72 of the X-rayhigh-voltage device 6, the conductive layer 651 and the conductive layer652 to the conductive layer 65 n may prevent the occurrence of coronadischarge and therefore it is not necessary to fill the space betweenwinding wires of the secondary coil I11 and the secondary coil I12 tothe secondary coil I1 n with resin. Thus, the manufacturing process ofthe high-voltage generators 71, 72 in the X-ray high-voltage device 6 issimplified. Furthermore, as the space between winding wires is notfilled with resin, the distributed capacitance between winding wires isnot increased.

Here, it may be considered that the distributed capacitance is acapacitor that is connected in parallel to each of the secondary coilI11 and the secondary coil I12 to the secondary coil I1 n. Therefore,the high-voltage generator in the X-ray high-voltage device 6 mayprevent an increase in the wattless current. Thus, the X-rayhigh-voltage device 6 may prevent overheating and efficiency degradationof the inverter.

Furthermore, if the high-voltage transformer, included in the X-rayhigh-voltage device 6, receives an input of the alternating current,which is close to the resonance frequency, it cannot be used as a normaltransformer due to an increase in the impedance. However, as describedabove, the high-voltage generators 71, 72 in the X-ray high-voltagedevice 6 may prevent an increase in the distributed capacitance of thesecondary coil I11 to the secondary coil I1 n. Therefore, the X-rayhigh-voltage device 6 may increase the frequency of the alternatingcurrent that is output from the inverter. Furthermore, this allows areduction in the size of the X-ray high-voltage device 6.

The conductive layer 65 n covers the high-voltage rectifying-smoothingcircuit 619 n. Furthermore, the conductive layer 65 n is conductive, andit is electrically connected to a single point of the high-voltagerectifying-smoothing circuit 619 n. For this reason, the electricpotential of the entire conductive layer 65 n is equal to the electricpotential at the single point of the high-voltage rectifying-smoothingcircuit 619 n. Therefore, the conductive layer 65 n may prevent damagesto the X-ray high-voltage device 6 due to the corona discharge thatoccurs between the high-voltage rectifying-smoothing circuit 619 n and adifferent component f the X-ray high-voltage device 6. This is becausethe difference between the maximal value and the minimum value of thevoltage, generated by the high-voltage rectifying-smoothing circuit 619n, is smaller than the potential difference generated by the coronadischarge.

Furthermore, the conductive layer 65 n may prevent corona discharge thatoccurs at corners of electronic components or leads, included in thehigh-voltage rectifying-smoothing circuit 6191 to the high-voltagerectifying-smoothing circuit 619 n. Therefore, it is not necessary toprocess corners of electronic components or leads so as to preventcorona discharge. Furthermore, corona discharge that occurs between theconductive layer 65 n and the high-voltage rectifying-smoothing circuit619 n may be prevented by increasing the distance between the conductivelayer 65 n and the high-voltage rectifying-smoothing circuit 619 n. Thesame holds for the conductive layer 651, the conductive layer 652, orthe like.

Furthermore, it is preferable that the surfaces of the conductive layer651 to the conductive layer 65 n are curved surfaces or plain surfaces.Specifically, it is preferable that any area on the surfaces of theconductive layer 651 to the conductive layer 65 n is a curved surface ora plain surface. This is because, if the conductive layer 651 to theconductive layer 65 n have a tapered area or a bent area, there is apossibility that electric field concentration occurs at these areas andcorona discharge occurs. Therefore, if the conductive layer 651 to theconductive layer 65 n are formed on the outer surfaces of the insulatinglayer 641 to the insulating layer 64 n, respectively, it is preferablethat the outer surfaces of the insulating layer 641 to the insulatinglayer 64 n are curved surfaces or plain surfaces.

Furthermore, in the high-voltage generators 71, 72 in the X-rayhigh-voltage device 6, all the secondary coils and the high-voltagerectifying-smoothing circuits, illustrated in FIG. 2, may not be coveredwith conductive layers. In this case, too, the high-voltage generators71, 72 in the X-ray high-voltage device 6 may prevent corona dischargethat occurs in the space between the winding wires of the secondarycoil, covered with the conductive layer, or corona discharge that occursbetween the high-voltage rectifying-smoothing circuit, covered with theconductive layer, and a different component of the high-voltagegenerators 71, 72 in the X-ray high-voltage device 6.

Furthermore, it is preferable that the secondary coil 711 and thehigh-voltage rectifying-smoothing circuit 6191. The same are coveredwith a single conductive layer rather than being individually coveredwith a conductive layer. This is because, if the secondary coil I11 andthe high-voltage rectifying-smoothing circuit 6191 are individuallycovered with a conductive layer, corona discharge sometimes occurs inthe conductive wire that connects the secondary coil I11 and thehigh-voltage rectifying-smoothing circuit 6191. The same holds for thesecondary coil I12 and the high-voltage rectifying-smoothing circuit6192 to the secondary coil I1 n and the high-voltagerectifying-smoothing circuit 619 n, the secondary coil I21 and thehigh-voltage rectifying-smoothing circuit 6291 and the secondary coilI22 and the high-voltage rectifying-smoothing circuit 6292 to thesecondary coil I2 n and the high-voltage rectifying-smoothing circuit629 n.

FIG. 9 is a diagram that illustrates an example of the configuration ofa medical-image diagnostic apparatus 1 that uses the X-ray high-voltagedevice 6 and the high-voltage generators 71, 72 according to the presentembodiment. The medical-image diagnostic apparatus 1 is for example anX-ray CT apparatus. As illustrated in FIG. 9, the medical-imagediagnostic apparatus 1 includes a gantry 2, a bed 20, and a console 30.Furthermore, the configuration of the medical-image diagnostic apparatus1 is not limited to the following configuration.

The gantry includes collimator adjustment circuitry 3, gantry drivecircuitry 4, the X-ray high-voltage device 6, the X-ray tube 7, a wedge8, a collimator 9, a detector 10, data acquisition circuitry 11, and arotary frame 12.

The collimator adjustment circuitry 3 adjusts the aperture and theposition of the collimator 9, thereby adjusting the irradiation range ofX-rays that are generated by the X-ray tube 7. The collimator adjustmentcircuitry 3 is connected to the collimator 9, and it includes themechanism that adjusts the aperture and the position and the circuitrythat controls the mechanism. The mechanism includes, for example, amotor and a mechanical element that transmits power, generated by themotor, to the collimator 9. Furthermore, the above-described circuitryincludes, for example, circuitry that feeds electric power or controlsignals to the motor and a processor that controls the circuitry.

The gantry drive circuitry 4 rotates the rotary frame 12, therebyrotating the-ray high-voltage device 6, the X-ray tube 7, and thedetector 10 on the circular orbit with a subject P at the center. Thegantry drive circuitry 4 is connected to the rotary frame 12, and itincludes a mechanism that rotates it and circuitry that controls themechanism. The mechanism includes, for example, a motor and a mechanicalelement that transmits power, generated by the motor, to the rotaryframe 12. Furthermore, the above-described circuitry includes, forexample, circuitry that feeds electric power or control signals to themotor and a processor that controls the circuitry.

The X-ray high-voltage device 6 generates a high voltage. The X-rayhigh-voltage device 6 includes the primary coils 616, 626, the secondarycoils I11 to I1 n, and the secondary coils I21 to I2 n. Furthermore, theX-ray high-voltage device 6 includes the high-voltagerectifying-smoothing circuits 6191 to 619 n, the high-voltagerectifying-smoothing circuits 6291 to 629 n, and the conductive layersthat cover them. Furthermore, the configurations of them are asdescribed above.

The X-ray tube 7 generates X-rays by using the high voltage that issupplied from the X-ray high-voltage device 6. The X-ray tube 7 includesa cathode, an anode, and a chassis. The cathode emits electrons. Theanode receives the electrons and generates X-rays. The chassis housesthe cathode and the anode. The inside of the chassis is a vacuum.

The wedge 8 is an X-ray filter that adjusts the dose of radiation andthe radiation quality of X-rays that are generated by the X-ray tube 7.

The collimator 9 is a slit for adjusting the irradiation range ofX-rays. The collimator 9 is made of material that may shield againstX-rays that are generated by the X-ray tube 7. The material is forexample lead. The aperture and the position of the collimator 9 areadjusted by the collimator adjustment circuitry

The detector 10 detects X-rays. The detector 10 includes multipledetecting elements. The detector 10 uses the detecting element to detectX-rays that are generated by the X-ray tube 7. The detecting elementconverts incident X-rays into electric signals and outputs the electricsignals to the data acquisition circuitry 11. The size, shape, andnumber of detecting elements, included in the detector 10, are notparticularly limited. Furthermore, the detector 10 may be either adirect-conversion type or an indirect-conversion type. The dataacquisition circuitry 11 generates projection data on the basis ofelectric signals that are output from the detecting element.

The rotary frame 12 is a circular frame. The rotary frame 12 supportsthe X-ray high-voltage device 6, the X-ray tube 7, and the detector 10.The X-ray tube 7 and the detector 10 are opposed to each other. Therotary frame 12 is driven by the gantry drive circuitry 4 to rotate withthe subject P at the center.

The bed 20 includes a top board 21 and bed drive circuitry 22. The topboard 21 is a plate-like member on which the subject P is placed. Thebed drive circuitry 22 moves the top board 21, on which the subject P isplaced, thereby moving the subject P within the capturing hole of thegantry 2.

The console 30 includes an input interface 31, a display 32, a memory33, and processing circuitry 34.

The input interface 31 is used by a user who inputs commands orsettings. The input interface 31 is configured by, for example, a mouseor a keyboard. The input interface 31 transfers commands or settings,input by a user, to the processing circuitry 34. The input interface 31is implemented by, for example, a processor.

The display 32 is a monitor that is viewed by a user. The display 32 is,for example, a liquid crystal display. The liquid crystal display is adisplay in which a polarization filter, a glass substrate, a transparentelectrode, an oriented film, a liquid crystal layer, a color filter, anda backlight are laminated. The display 32 receives, from the processingcircuitry 34, the commands to display for example CT images or theGraphical User Interface (GUI), which is used by a user to inputcommands or settings. The display 32 presents CT images or the GUI inaccordance with the commands.

The memory 33 stores raw data generated by a preprocessing function 342that is described later, CT images generated by an image generationfunction 343 that is described later, and programs for the collimatoradjustment circuitry 3, the gantry drive circuitry 4, and the dataacquisition circuitry 11 to implement the above-described functions. Thememory 33 stores a program for the bed drive circuitry 22 to implementthe above-described function. The memory 33 stores programs for theprocessing circuitry 34 to implement a scan control function 341, thepreprocessing function 342, the image generation function 343, a displaycontrol function 344, a control function 345, described later, and otherfunctions. Therefore, the collimator adjustment circuitry 3, the gantrydrive circuitry 4, the data acquisition circuitry 11, the bed drivecircuitry 22, and the processing circuitry 34 read and execute programsthat are stored in the memory 33, thereby performing the functions.

Furthermore, the memory 33 includes a storage medium that may readstored information by using a computer. The storage medium is, forexample, a hard disk.

The processing circuitry 34 includes the scan control function 341, thepreprocessing function 342, the image generation function 343, thedisplay control function 344, and the control function 345. Theprocessing circuitry 34 is implemented by, for example, a processor.

The scan control function 341 is a function that controls themedical-image diagnostic apparatus 1 so as perform scanning. Theprocessing circuitry 34 reads the program, which corresponds to the scancontrol function 341, from the memory 33 and executes it, therebycontrolling the medical-image diagnostic apparatus 1 as described belowfor example.

The processing circuitry 34 controls the bed drive circuitry 22 so as tomove the subject P into the capturing hole of the gantry 2. Here, thecapturing hole is a hollow that is provided inside the trajectory withwhich the X-ray tube 7 and the rotary frame 12 rotate. The processingcircuitry 34 causes the gantry 2 to perform scanning on the subject P.Specifically, the processing circuitry 34 controls the X-rayhigh-voltage device 6 so as to supply a high voltage to the X-ray tube7. The processing circuitry 34 controls the collimator adjustmentcircuitry 3 so as to adjust the aperture and the position of thecollimator 9. Furthermore, the processing circuitry 34 controls thegantry drive circuitry 4 so as to rotate the rotary frame 12Furthermore, the processing circuitry 34 controls the data acquisitioncircuitry 11 so as to make the data acquisition circuitry 11 acquireprojection data. The scan executed by the medical-image diagnosticapparatus 1 is, for example, conventional scan, helical scan, orstep-and-shoot.

The preprocessing function 342 is a function to correct projection datathat is generated by the data acquisition circuitry 11. The processingcircuitry 34 reads the program, which corresponds to the preprocessingfunction 342, from the memory 33 and executes it, thereby correcting theprojection data. The correction is, for example, logarithmic conversion,offset correction, sensitivity correction, beam hardening correction, orscattered ray correction. The projection data, corrected by thepreprocessing function 342, is stored in the memory 33. Furthermore, theprojection data, corrected by the preprocessing function 342, is alsocalled raw data.

The image generation function 343 is a function to reconstruct raw data,stored in the memory 33, and generate a CT image. The processingcircuitry 34 reads the program, which corresponds to the imagegeneration function 343, from the memory 33 and executes it, therebygenerating a CT image. The reconstruction method is, for example, a backprojection process or a successive approximation technique. CT images,generated by the image generation function 343, are stored in the memory33.

The display control function 344 is a function to present CT images,stored in the memory 33, on the display 32. The processing circuitry 34reads the program, which corresponds to the display control function344, from the memory 33 and executes it, thereby presenting CT images,stored in the memory 33, on the display 32.

The control function 345 includes a function to operate each componentof the gantry 2, the bed 20, and the console 30 at appropriate timing inaccordance with a purpose and includes other functions. To perform theabove-described process, the processing circuitry 34 reads the program,which corresponds to the control function 345, from the memory 33 andexecutes it as appropriate.

The medical-image diagnostic apparatus 1 may be an apparatus other thanthe X-ray CT apparatus. The medical-image diagnostic apparatus 1 may be,for example, an X-ray diagnostic apparatus. The X-ray diagnosticapparatus is, for example, a C-arm type X-ray diagnostic apparatus or anX-ray TV apparatus. The C-arm type X-ray diagnostic apparatus is usedfor capturing of X-ray fluoroscopic images of a subject. The X-ray TVapparatus is used for, for example, gastrointestinal tract contrastexamination, urinary tract contrast examination, spinal cord cavitycontrast examination, or biliary tract contrast examination.

The above-described processor is, for example, a central processingunit. (CPU), a graphics processing unit (GPU), an application specificintegrated circuit (ASIC), a programmable logic device (PLD), or a fieldprogrammable gate array (FPGA). Furthermore, the programmable logicdevice (PLD) is, for example, a simple programmable logic device (SPLD)or a complex programmable logic device (CPLD).

According to the above-described embodiment, the collimator adjustmentcircuitry 3, the gantry drive circuitry 4, the data acquisitioncircuitry 11, the bed drive circuitry 2, and the processing circuitry 34read programs, stored in the memory 33, and execute them to implementtheir functions; however, this is not a limitation. Instead of storingprograms in the memory 33, a program may be directly installed in eachof the circuitry. In this case, the circuitry reads the directlyinstalled programs and execute them to implement their functions.

The circuits, illustrated in FIG. 9, may be separated or combined asappropriate. For example, the processing circuitry 34 may be separatedinto scan control circuitry, preprocessing circuitry, image generationcircuitry, display control circuitry, and control circuitry thatimplement functions, such as the scan control function 341, thepreprocessing function 342, the image generation function 343, thedisplay control function 344, and the control function 345. Furthermore,for example, the collimator adjustment circuitry 3, the gantry drivecircuitry 4, the data acquisition circuitry 11, the bed drive circuitry22, and the processing circuitry 34 may be combined optionally.

According to at least one of the above-described embodiments, it ispossible to provide a medical-image diagnostic apparatus and an X-rayhigh-voltage device, with which corona discharge may he prevented.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A high-voltage device comprising: An inverter circuit configured to convert a direct-current voltage into an alternating-current voltage; a high-voltage transformer including a primary coil on an input side and multiple secondary coils on an output side and raising a voltage of output of the inverter circuit; an insulating layer provided on an outer circumference of a bundle of winding wires of each of the secondary coils so as to individually cover each of the secondary coils; and a conductive layer provided on an outer circumference of each of the insulating layers so as to individually cover each of the insulating layers.
 2. The high-voltage device according to claim 1, further comprising a high-voltage rectifying-smoothing circuit configured to rectify output of the high-voltage transformer, wherein the insulating layer is provided to further cover the high-voltage rectifying-smoothing circuit in addition to the secondary coil, and the conductive layer is provided on circumferences of both the secondary coil and the high-voltage rectifying-smoothing circuit with the insulating layer interposed.
 3. The high-voltage device according to claim 2, wherein the insulating layer is a container made of insulating material to house at least one of the secondary coil and the high-voltage rectifying-smoothing circuit.
 4. The high-voltage device according to claim 1, wherein the conductive layer covers an entire surface of the high-voltage rectifying-smoothing circuit and electrically connects to a single point of the high-voltage rectifying-smoothing circuit.
 5. The high-voltage device according to claim 4, wherein the conductive layer is electrically connected to an input terminal of the high-voltage rectifying-smoothing circuit.
 6. The high-voltage device according to claim 4, wherein the conductive layer is electrically connected to an output terminal of the high-voltage rectifying-smoothing circuit.
 7. The high-voltage device according to claim 2, wherein an outer surface of the insulating layer is a curved surface or a plain surface, and the conductive layer is formed on the outer surface of the insulating layer.
 8. A medical-image diagnostic apparatus comprising: a high-voltage device generating a high voltage; and an X-ray tube generating an X-ray by using the high voltage supplied from the high-voltage device, wherein the high-voltage device comprises an inverter circuit converting a direct-current voltage into an alternating-current voltage; a high-voltage transformer including a primary coil on an input side and multiple secondary coils on an output side and raising a voltage of output of the inverter circuit; an insulating layer provided on an outer circumference of a bundle of winding wires of each of the secondary coils so as to individually cover each of the secondary coils; and a conductive layer provided on an outer circumference of each of the insulating layers so as to individually cover each of the insulating layers. 